Reactions of carbonyl compounds with tervalent phosphorus reagents. Part 10. Monochlorophosphines and aldehydes

Abstract

The reaction of chlorophosphines (1) with aldehydes to give α-chloroalkylphosphine oxides (11) has been shown to involve two stable organophosphorus intermediates. Detailed study of the reaction of chlorodiphenylphosphine (1a) with benzaldehyde has revealed that the intermediates are α-chlorobenzyl α-(diphenylphosphinoyl)benzyl ether (8a) and bis-[α-(diphenylphosphinoyl)benzyl] ether (12a), and that each is formed as one diastereoisomer only. 2-Chloro-2,2,3,5-tetraphenyl-1,4,2λ⁵-dioxaphospholan (4a) is suggested as the precursor of these phosphine oxides, and experimental evidence for the overall pathway to α-chlorobenzyldiphenylphosphine oxide (11a) is presented. Previous rationalisations of these complex reactions are shown to need reappraisal.